The Saskatchewan REALTORS Association's benchmark home price of $444,700 gives a sense of scale for the market a suite sits inside, but it measures sale prices, not rents, so it cannot be converted into a rent figure directly. CMHC's rental market reporting is the closer source, though it does not break results down to the suite level.
Legality decides more of the answer than size does. A permitted secondary suite, with a separate entrance, proper egress windows and fire separation confirmed by the City of Saskatoon, rents to a wider pool of tenants and finances differently than an unpermitted space a landlord cannot advertise honestly.
The realistic number for your specific basement or garden suite comes from comparable listings for a unit in similar condition nearby. Get your hand-reviewed valuation from Joel Dyck.